Manufacture of artificial silk and like products



Patented Aug. 25, 1936 PATENT OFFICE MANUFACTURE OF ARTIFICIAL SILK AND LIKE PRODUCTS Henry Dreyfus, London, England No Drawing. Application September "I, 1933, Serial No. 688,499

9 Claims.

This application is a continuation in part of U. S. application S. No. 638,776 filed 20th October, 1932 and relates to improvements in artificial silk and like products and processes for their manufacture and is particularly addressed to the problem of stretching such artificial filaments and like products for thepurpose of increasing their tenacity, reducing their denier and increasing their resistance to the delustring action of hot aqueous liquids.

In said U. S. application S. No. 638,776 I have described how artificial filaments and like products may be softened and stretched to yield products of improved properties. According to this prior application the formed materials are softened by subjecting them to the action of a softening agent having a relatively low solvent or softening action and then with a softening agent having a high solvent or softening action. By this process it was found .that the amount of stretching might be improved in a very remarkable manner.

It has now been found that not only does the process described in the above application yield improved results, but that broadly the use of two or more softening treatments of different strengths is of value in processes of stretching artificial materials containing organic derivatives of cellulose.

According to the present inverition the softening treatment used to produce the degree of softening requisite for the stretching'process is preceded by one or more softening or swelling treatments. In general the strength of the softening treatment or treatments preceding the final softening treatment will be such as to produce a degree of softening of the materials less, but preferably only slightly less, than that effected in the final softening treatment. The invention does not, however, excludethe use of pretreatments capable of producing a higher degree of softening than is desired in the final softening treatment, for example by the use of baths of higher concentrations or of higher temperatures, provided that such pretreatments are applied for such periods of time or under such other conditions that deleteriousaction on the materials does not result.

The term strength where employed in relation to swelling treatments is to be understood as referring to the degree of swelling produced in the materials under treatment by the particular treatment employed.

Various methods may be employed in carrying out the process of the present invention. For

example the filaments or other products may be subjected in conjunction with astretching operation to a succession of softening treatments, at least one of these treatments, and preferably the final one, being of greater strength than a preceding treatment. Thus the filaments or other materials may be subjected to a succession of softening treatments of progressively increasing strength. In general it is found sufiicient to employ two softening treatments, the second be- 10 ing of greater strength thanthe first. It is found that the use of two treatments, the first of which is of only slightly lower strength than the second, yields particularly valuable results.

Variation in strength of softening treatments may be secured by altering the nature, quantity, concentration, or temperature of the softening agent used or the duration of its action on the materials. It will be appreciated that two or more of these factors may simultaneously be altered. Thus a succession of treatments with the same reagent in progressively increasing concentration may be employed, or the concentration of the reagent may remain constant and the temperature may be varied in order to alter the strength of the softening treatment, as for example by applying the first treatmentor earlier treatments at room temperature or below, e. g. from 5-10 or more below, and the succeeding or final treatment or treatments at slightly higher temperatures. ,Again, the duration of the successive treatments may be different so as to vary the strength of the different treatments.

As indicated above, any two or more of these methods of varying the strength of successive treatments may be employed, for example both concentration and temperature may be different in one treatment as compared with another. Thus they may both be higher in one case or one may be higher and the other lower.

The treatments may be applied to the materials in any suitable form, for example in the form of hanks, cones, bobbins or other packages, or during their travel from one point to another, or part of the process may be applied to the 'materials in package form and part during the course of their travel from point to point. The times of the different treatments may vary within wide limits, for example from a few minutes to several hours, depending, inter alia, on the other conditions prevailing.

Salts, sugars or other substances, as described in U. S. applications S. Nos. 638,179 filed 17th October, 1932 and 636,943 filed 8th October, 1932 55 ticular value in the treatment of artificial filaments and the like of heavy denier and also of artificial materials obtained from cellulose acetate or other cellulose derivatives of medium or high viscosity. The actual stretching of the filaments may be conducted while: the filaments are in hank form, but is preferably effected on the travelling filaments, as described in my U. S. application S. No. 378,68 i filed 16th July, 1929, for example in bobbin to bobbin operations, or in the transit of the filaments from a spinning apparatus to a winding device. It may also be applied to filaments in the form of a warp, as is described in U. S. application S. No. 602,844 filed 2nd April, 1932. Moreover, the stretch may be inserted in one stage and preferably very gradually, or may, as described in U. S. application S. No. 573,424 filed 6th November, 1931, be inserted in a number of stages with a rest period between each. It is preferable that the solvent be not removed from the materials during the rest period. In working a multi-stage stretching operation in accordance with the present invention, it is not necessary to subject the materials to the whole succession of softening treatments at each stage, since in general one or a small number of treatments is sufiicient to maintain the materials in a softened condition.

As suitable solvents or softening agents for use in the present invention the following may be mentioned:aqueous solutions of thiocyanates, such as those of the alkalies, ammonia and alkaline earths, aqueous solutions of zinc chloride; acetic acid, formic acid, lactic acid, diacetone alcohol, acetone and the like; the ethers and esters and ether-esters of olefine and polyolefine glycols, for instance the monoand dimethyl and ethyl ethers of ethylene glycol, the internal ether of ethylene glycol namely dioxane, methylene ethylene ether, the mono-methyl and ethyl ethers of propylene glycol, the mono-ethyl ether of diethylene glycol, the mono-esters of ethylene glycol, as for instance glycol-mono-acetate, and the ether-esters of ethylene glycol, for instance methyl glycol mono-acetate; phenols, formaldehyde, acetaldehyde, monoand di-acetins, dichlorethylene, ethylene chloride, methylene chloride and the like or mixtures of these or solvent mixtures. Such solvents or softening agents may be diluted with water or with organic diluents, for example aliphatic, aromatic or cyclo-aliphatic hydrocarbons, alcohols, isopropyl ether or other ethers and certain non-solvent chlorinated hydrocarbons, for instance carbon tetrachloride.

The optimum concentration for any particular solvent for the final softening treatment of course varies considerably. For acetone in aqueous solution it is usually 40% with the commercial acetone-soluble cellulose acetate, with aqueous acetic acid it is about 42.5%, while with dioxane, ethyl lactate and diacetone alcohol concentrations of 40 to 50% are especially valuable. .With any of these agents the treatment of lower strength is preferably effected with the solvent in only slightly lower concentration, e. g. 3-5 or 7% lower, than in the treatment of higher strength.

The following examples are given by way of illustration only and it is to be clearly understood that they do not limit the invention in any way:-

Example 1 Example 2 A cellulose acetate yarn proceeding from a dry spinning apparatus or from a bobbin orother suitable package is passed through a bath containing an aqueous solution of ethyl lactate in about 45% concentration and is then stretched while passing through another similar bath in which the concentration is about 50%. After stretching the yarn is washed, e. g. with a dilute solution of ethyl lactate, dried and wound on bobbin or other suitable support. The invention is of particular importance in the treatment of filaments and like products of cellulose acetate but it may also be applied with valuable results to the treatment of products of other cellulose esters or mixed esters, for example cellulose formate, cellulose propionate, cellulose butyrate and nitroacetate, ethyl, butyl and benzyl cellulose and other cellulose ethers or mixed ethers and cellulose ether-esters, for ex ample ethyl cellulose acetate and oxy-ethyl cellulose acetate.

The terms swelling treatment and swelling where employed hereinafter in the claims are to be understood to mean the treatment with, and the swelling produced by, solvents or other swelling agents as described above.

Having described my invention what I claim and desire to secure by Letters Patent is:-

1. Process for the treatment of artificial filaments, threads, yarns, ribbons and like artificial materials containing organic derivatives of cellulose, which comprises softening said materials by at least two treatments with swelling media of successively increasing strength, the penultimate treatment being of only slightly lower strength than the ultimate treatment, and stretching the materials by applying tension thereto only when they are swollen by the ultimate swelling treatment.

2. Process for the treatment of artificial filaments, threads, yarns, ribbons and like artificial materials containing organic derivatives of cellulose, which comprises softening said materials by at least two treatments with swelling media of successively increasing strength, the treatments being carried out at different temperatures and the penultimate treatment being of only tension thereto only when they are swollen by the ultimate swelling treatment.

3. Process for the treatment of artificial filaments, threads, yarns, ribbons and like artificial materials containing organic derivatives of cellulose, which comprises softening said materials by at least two treatments with swelling media of successively increasing strength, the treatments being carried out with baths containing the same concentration of swelling agent at different temperatures and the penultimate treatment being of only slightly lower strength than the ultimate treatment, and stretching the materials by applying tension theretoonly when they are swollen by the ultimate swelling treatment.

slightly lower strength than the ultimate treatment, and stretching the materials by applying 4. Process for the treatment of artificial filaments, threads, yarns, ribbons and like artificial materials containing organic derivatives of cellulose, which comprises softening said materials by at least two treatments with swelling media of successively increasing strength, the treatments being carried out with baths containing difierent concentrations of swelling agent and the penultimate bath being 2-'7% lower in concentration than the ultimate treatment, and stretching the materials by applying tension thereto only when they are swollen by the ultimate swelling treatment.

5. Process for the treatment of artificial filaments, threads, yarns, ribbons and like artificial materials containing organic derivatives of cellulose, which comprises softening said materials by two treatments with the same swelling agent in difierent concentrations, the first treatment being effected with the swelling agent in 2-7% lower concentration than the second treatment, and stretching the materials by applying tension thereto only when they are swollen 'by the second swelling treatment.

6. Process for the treatment of artificial filaments, threads, yarns, ribbons and like artificial materials containing organic derivatives of cellulose, which comprises softening said materials by at least two treatments with swelling media of successively increasing strength, the treatments being carried out with baths containing different concentrations of swelling agent and the penultimate treatment being effected with a bath of swelling agent -2-7% lower in concentration than said ultimate treatment, and stretching the ma terials by applying tension thereto only when they are swollen by the ultimate swelling treatment, the swelling agent employed being selected from the group consisting of acetone, acetic acid, dioxane, ethyl lactate and diacetone alcohol.

7. Process for the treatment of artificial filaments, threads, yarns, ribbons and like artificial materials containing organic derivatives of cellulose,'which comprises softening said materials by at least two treatments with swelling media of successively increasing strength, the ultimate treatment being effected with a bath of swelling agent of 40-50% concentration in an aqueous medium and the penultimate treatment being effected with a bath of swelling agent 2-'7% lower in concentration than said. ultimate treatment, and stretching the materials by applying tension thereto only when they are swollen by the ultimate swelling treatment, the swelling agents employed 1 being selected from the group consisting of acetone, acetic acid, dioxane, ethyl lactate and diacetone alcohol.

8. Process for the treatment of artificial filaments, threads, yarns, ribbons and like artificial 1 materials containing organic derivatives of cellulose, which comprises softening said materials by at least two treatments with swelling media of successively increasing strength, the treatments being carried out with baths containing the same 2 concentration of the same swelling agent at different temperatures, the penultimate treatment being at a lower temperature and of only slightly lower strength than the ultimate treatment, and stretching the materials by applying tension 2 thereto only when they are swollen by the ultimate swelling treatment, the swelling agents em-. 'ployed being selected from the group consisting of acetone, acetic acid, dioxane, ethyl lactate and diacetone alcohol. 3

9. Process for the treatment of artificial 'filaments, threads, yarns, ribbons and like artificial materials containing organic derivatives of cellulose, which comprises softening said materials by at least two treatments with swelling media of successively increasing strength, the ultimate treatment being efiected with a bath of swelling agent of 40-50% concentration and the penultimate treatment being of only slightly lower strength than the ultimate treatment, and stretching the materials by applying tension thereto only when they are swollen by the ultimate swelling treatment.

HENRY. DREYFUS. 

